Name: synthesis of substrate-bound au nanowires via an active surface growth mechanism
Uploaded: 2018-07-18T15:00:00
Description: Watch this Scientific Journal Video about Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism at JoVE.com

We gratefully acknowledge the financial support from National Natural Science Foundation of China (21703104), Jiangsu Science and Technology Plan (SBK2017041514) Nanjing Tech University (39837131), and SICAM Fellowship from Jiangsu National Synergetic Innovation Center for Advanced Materials.

Caution: Please check the material safety data sheets (MSDS) of the chemicals for detailed handling and storage instruction. Please be careful while handling the nanomaterials, as there may be unidentified risk. Please perform the experiments in a fume hood and wear appropriate personal protective equipment.
1. Synthesis of Seed Nanoparticles
Note: To avoid failure caused by the premature nucleation during the nanoparticle synthesis, wash the glassware and stir bar us...

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The mechanism of this active surface growth governed nanowire synthesis has been discussed comprehensively in previous work19. In addition, the effects of seed sizes and types as well as the effect of ligand types and sizes have also been investigated20,21. Generally. the nanowire growth is very different from previous reported routes. No template is required, and the asymmetric growth is induced by the differences between the ligand-cappe...

Typical of one dimensional nanomaterials, nanowires possess both the bulk-related properties and the unique properties originated from the quantum effects of the nanoscale structure. As a bridge between the nanoscale and the bulk scale materials, they have been widely applied in various fields of catalysis, sensing, and nanoelectronic devices, etc.1,2,3.
However, the synthesis of nanowires has long been a great challenge, as it usually requires breaking the intrinsic symmetry in the crystals. Traditionally, a template is employed to regulate the deposition of materials. For instance, template-electrodeposition has been used for the formation of various types of nanowires like Ag nanowires and CdS nanowires4,5,6,7,8,9,10. Another common approach is vapor-liquid-solid (VLS) growth, which employs a molten catalyst to induce the anisotropic growth on the substrate at an elevated temperature11. Common strategies for the synthesis of metal nanowires are the polyol methods for Ag nanowires and the oleylamine-assisted ultrathin Au nanowires12,13,14,15. Both approaches are material-specific, and the nanowire parameters are not readily tuned during the synthesis. In addition, metal nanowires can also be formed by the pressure-driven method, where the assembled metal nanoparticles are mechanically compressed and fused into nanowires16,17,18.
Recently, we reported a distinctive method to synthesis Au nanowires19. With the assist of a thiolated small molecule ligand, the nanowires could grow and form a vertically aligned array on the bulk Si wafer substrate at ambient conditions. It was found that the ligands play an important role in the symmetry-breaking growth. It binds to the surface of the substrate-adsorbed Au seeds strongly, forcing the Au to deposit selectively at the ligand-deficient interface between seeds and substrate. The interface between the newly deposited Au and the substrate remains ligand deficient, therefore, the active surface exists throughout the whole growth. By tuning the ligand concentration, the seed type and concentration as well as several other parameters, a series of Au nanowire-based nanostructures could be synthesized.
In this work, we will provide a detailed protocol for this convenient Au nanowires synthesis. The derived synthesis is also presented, including the synthesis of Au nanowires with hydrophobic surface property, Au nanowires on other substrates, tapered Au nanowires by mixing two ligands and the nanowire-based Au nanostructures formed by tuning the growth conditions.

<table border="0" cellpadding="0" cellspacing="0" width="846">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Trisodium citrate dihydrate</td>
			<td style="width:209px;">Alfa Aesar</td>
			<td style="width:179px;">LoT: 5008F14U</td>
			<td style="width:203px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium borohydride</td>
			<td style="width:209px;">Fluka</td>
			<td style="width:179px;">LoT: STBG0330V</td>
			<td>NaBH4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hydrogen tetrachloroaurate(III) trihydrate</td>
			<td style="width:209px;">Alfa Aesar</td>
			<td style="width:179px;">LoT: T19C006</td>
			<td style="width:203px;">HAuCl4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3-aminopropyltriethoxysilane</td>
			<td style="width:209px;">J&#38;K Scientific</td>
			<td style="width:179px;">LoT: LT20Q102</td>
			<td style="width:203px;">APTES</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">L-ascorbic acid&#160;</td>
			<td>Sigma-Aldrich</td>
			<td style="width:179px;">LoT: SLBL9227V</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4-mercaptobenzoic acid</td>
			<td>Sigma-Aldrich</td>
			<td style="width:179px;">LoT: MKBV5048V</td>
			<td style="width:203px;">4-MBA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-Naphthalenethiol</td>
			<td>Sigma-Aldrich</td>
			<td style="width:179px;">LoT: BCBP4238V</td>
			<td>2-NpSH</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4-Mercaptophenylacetic acid</td>
			<td style="width:209px;">Alfa Aesar</td>
			<td style="width:179px;">LoT: 10199160</td>
			<td>4-MPAA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3-mercaptobenzoic acid</td>
			<td style="width:209px;">Aladdin</td>
			<td style="width:179px;">LoT: G1213027</td>
			<td>3-MBA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3-Mercaptopropionic acid</td>
			<td style="width:209px;">Aladdin</td>
			<td style="width:179px;">LoT: E1618095</td>
			<td>3-MPA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">absolute ethanol</td>
			<td style="width:209px;">Sinopharm chemical Reagent</td>
			<td style="width:179px;">20170802</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Silicon wafer</td>
			<td style="width:209px;">Zhe Jiang lijing</td>
			<td style="width:179px;">P</td>
			<td>Si</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scanning Electron Microscope</td>
			<td style="width:209px;">Quanta FEG 250</td>
			<td style="width:179px;"></td>
			<td>SEM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge&#160;</td>
			<td style="width:209px;">Eppendorf</td>
			<td style="width:179px;">5424</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic cleaner&#160;</td>
			<td style="width:209px;">Kun Shan hechuang</td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Ultra-pure water system</td>
			<td style="width:209px;">NanJing qianyan</td>
			<td style="width:179px;">UP6682-10-11</td>
			<td>for deionized water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Plasma cleaner</td>
			<td style="width:209px;">Harrick Plasma</td>
			<td style="width:179px;">PDC-002</td>
			<td>for oxygen plasma</td>
		</tr>
	</tbody>
</table>

synthesis of substrate-bound au nanowires via an active surface growth mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

The Au nanoparticle seeds, substrate-bound Au nanowires and Au nanowire-based derivative nanostructures are characterized with SEM. Figure 1 shows the representative SEM images of the 3-5 nm Au nanoparticles, 15 nm Au Nanoparticles and 40 nm Au nanoparticles adsorbed on the Si wafer, confirming their sizes, adsorption and distribution. The Au nanowires grown from the respective seeds on the Si wafer substrate are also presented. The representative SEM images ...

Watch this Scientific Journal Video about Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism at JoVE.com

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

This time I introduce using for generating one-dimensional nanostructure. The main advantage of this technique is that you can trace nano-wire, a long temperature under mild conditions with simple wet chemistry operations. First in a four-milliliter vial, dissolve 10 milligrams of hydrogen tetrachloroauric trihydrate in one milliliter of deionized water.By PET 0.197 milliliters of this 2.5 millimolar chloroauric acid stock solution into a 50-milliliter round bottom flask equipped with a stir bar. Add 19.7 milliliters of deionized water to the flask and stir to obtain a 0.025-millimolar chloroauric acid solution. Then in another four-milliliter vial, dissolve 10 milligrams of trisodium citrate dihydrate in one milliliter of deionized water.Add 0.147 milliliters of this 0.1-gram-per-milliliter sodium citrate stock solution to the diluted chloroauric acid solution while stirring. Next in a third four-milliliter vial dissolve 2.3 milligrams of sodium borohydride and 0.6 milliliters of deionized water to obtain a 0.1-molar solution which should be used within a few minutes. Ensure that the pale yellow reaction mixture is stirring vigorously.Quickly pipette the sodium borohydride solution into the vigorously stirring mixture which will immediately become bright orange. Continue stirring the mixture for 10 minutes to obtain the gold nanoparticles as indicated by a gradual color change to reddish-orange. The nano articles can be stored for up to a week.To synthesize gold nanowires, first cut a five-milliliter-by-five-milliliter piece from a 0.5 milliliter-thick silicon wafer. Sonicate this substrate for 15 minutes each in deionized water and ethanol in sequence. Wipe off the clean substrate and allow it to dry in air.Then treat the substrate with oxygen plasma at 29.6 watts and 220 volts for 20 minutes. During the plasma treatment, in a 20-milliliter vial, dissolve 11.1 milligrams of APTES in 10 milliliters of a one-to-one by volume mixture of deionized water and ethanol to obtain a 5-millimolar solution. When the plasma treatment has finished, soak the substrate in the APTES solution for 30 minutes.Then thoroughly rinse the substrate with about 20 milliliters each of ethanol and deionized water in sequence. Soak the substrate in the gold nanoparticle solution for two hours to allow the seed nanoparticles to absorb onto its surface. Then prepare 10 milliliters each of a 1.65-millimolar solution of 4-MBA and ethanol.Add 5.10 millimolars solution of chloroauric acid in a one-to-one mixture of deionized water and ethanol Add a 12.3 millimolar solution of L-ascorbic acid in deionized water. Combine 0.5 milliliters each of the chloroauric acid solution and the 4-MBA solution in a 10-milliliter vial. Shake the vial to mix the solutions.Next pick up the seeded substrate with tweezers and wash it with 20 milliliters of deionized water to remove unabsorbed gold nanoparticles. Immerse the seeded substrate in the mixture of chloroauric acid in 4-MBA. Then add 0.5 milliliters of the ascorbic acid solution to the mixture.Gently shake the vial to evenly mix the solutions. Leave the substrate soaking in the mixture undisturbed for 15 minutes. The air ascorbic acid must be added after the mixing of 4-MBA and chloroauric acid otherwise it will cause immediate homogeneous nucleation and the nanowires will not grow.Monitor the formation of bubbles during the growth process. The substrate surface will change from shiny gray to reddish-brown in appearance. Then remove the substrate from the mixture and rinse it with ethanol and deionized water.Allow it to air dry afterwards. The substrate surface will become a golden appearance as it dries. To synthesize gold nanowires with alternating segments of different thicknesses, first seed gold nanoparticles on a silicon substrate as previously described.Also prepare 10 milliliters each of a 1.65-millimolar 4-MBA solution, a 5.10-millimolar chloroauric acid solution, and a 12.3-millimolar ascorbic acid solution as previously described. Then dilute 0.1 milliliters of the 1.6-millimolar 4-MBA solution, 20-fold with ethanol to make two milliliters of a 0.083-millimolar 4-MBA solution. In a 10-milliliter vial, combine 0.5 milliliters each of the 1.65-millimolar solution of 4-MBA, the chloroauric acid solution and the ascorbic solution.Vortex the mixture to form growth solution A.In another 10-milliliter vial, combine 0.5 milliliters each of the 0.083-millimolar solution of 4-MBA, the chloroauric acid, and the ascorbic acid solution. Vortex the mixture to obtain growth solution B.Soak the gold nanoparticle seeded substrate and growth solution B for about one minute. Rapidly transfer the substrate to the container of growth solution A and allow it to soak for two minutes.Repeat the soaking sequence once being careful not to let the substrate dry as it is moved between vials. Finally rinse the substrate with 50 milliliters of ethanol and 50 milliliters of deionized water. Gold nanoparticle with diameters of three to five nanometers, 15 nanometers, and 40 nanometers were all successfully seeded on silicon wafer substrates.Substrate-bound gold nanowires were then grown from these seeds with 4-MBA as the ligand. Gold nanowires were also successfully grown on alumina, strontium titanate, lanthanum aluminate, glass, indium tin oxide, and fluorine-doped tin oxide surfaces. Nanowires with alternating thick-thin segments were grown by alternately immersing the substrate in growth solutions with different ligand concentrations.And nanoflowers were grown by quickly drying the growth solution on the silicon substrate. The nanowire structures could also be changed by varying the ligand. Using 4-MPAA, 2-naphthalenethiol, or 3-MBA as the ligand, yielded ultra-thin nanowires arrays.Using mixtures of 4-MBA and 3-MBA in various proportions yielded tapered nanowires. After watching this video, you should have a good understanding of how to grow growth nanowires from a foreign substrate with at the surface growth mechanism.

synthesis-substrate-bound-au-nanowires-via-an-active-surface-growth

Research

JoVE Journal

Chemistry

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the reaction is commonly performed using chlorinated or amide solvent systems, which are hazardous to human health and the environment. Our methodology utilizes acetonitrile as a greener and less hazardous solvent system. This protocol exhibits rates and yields that are comparable to traditional solvent systems and employs an extraction and wash sequence that eliminates the need for the purification of the ester product via column chromatography. This general method can be used to couple a variety of carboxylic acids with 1&#176; and 2&#176; aliphatic alcohols, benzylic and allylic alcohols, and phenols to obtain pure esters in high yields. The goal of the protocol detailed here is to provide a greener alternative to a common esterification reaction, which could serve useful for ester synthesis in both academic and industrial applications.

A modified Steglich esterification reaction was used to synthesize a small library of ester derivatives with primary and secondary alcohols. The methodology uses a non-halogenated and greener solvent, acetonitrile, and enables product isolation in high yields without the need for chromatographic purification.

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the ...

Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock copolymers are produced by one of three techniques: thin film rehydration, solvent switching or polymerization-induced self-assembly, and produce only flexible, polydisperse cylinders. Crystallization-driven self-assembly (CDSA) is a method which can produce cylinders with these properties, by stabilizing structures of a lower curvature due to the formation of a crystalline core. However, the living polymerization techniques by which most core-forming blocks are formed are not trivial processes and the CDSA process may yield unsatisfactory results if carried out incorrectly. Here, the synthesis of cylindrical nanoparticles from simple reagents is shown. The drying and purification of reagents prior to a ring-opening polymerization of &#949;-caprolactone catalyzed by diphenyl phosphate is described. This polymer is then chain extended by methyl methacrylate (MMA) followed by N,N-dimethyl acrylamide (DMA) using reversible addition&#8722;fragmentation chain-transfer (RAFT) polymerization, affording a triblock copolymer that can undergo CDSA in ethanol. The living CDSA process is outlined, the results of which yield cylindrical nanoparticles up to 500 nm in length and a length dispersity as low as 1.05. It is anticipated that these protocols will allow others to produce cylindrical nanostructures and elevate the field of CDSA in the future.

Crystallization-driven self-assembly (CDSA) displays the unique ability to fabricate cylindrical nanostructures of narrow length distributions. The organocatalyzed ring-opening polymerization of &#949;-caprolactone and subsequent chain extensions of methyl methacrylate and N,N-dimethyl acrylamide are demonstrated. A living CDSA protocol that produces monodisperse cylinders up to 500 nm in length is outlined.

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock ...